Bedfordshire North East MP Alistair Burt is to stand down from his frontbench role as Health Minister.
Mr Burt told MPs his decision had nothing to do with Brexit.
He informed David Cameron and Jeremy Hunt “a few weeks ago” that he would not be seeking a position in a reshuffled government.
He said he intends to continue his duties until September.
Raising a point of order at the end of health questions in the House of Commons, Mr Burt said: “Twenty-four years and one month ago I answered my first question as a junior minister in the House in oral questions and I have just completed my last oral questions.
A few weeks ago I made clear to the Secretary of State and to the Prime Minister and the Chief Whip that I wouldn’t after the referendum be seeking a post in what I expected to be a reshuffled government and in the event I hope to carry on with my duties until September, but there won’t be another oral questions.”